Gymnastic structures provided for children in the past have been heretofore constructed with reticulated structures the elements of the assembly forming three dimensional cells have been lengths of metal pipe provided with reverse threading on the opposite ends thereof which are joined to metal fittings having sockets with reverse threading thereon to form corners of the cells. Such a manner of connecting the elements of the assembly limits the ability of an adult to readily modify the structure of the assembly after it has once been assembled.